Previous elevator door systems employing single-sided linear induction motors typically generate large attractive forces between the motor primary and secondary. The large attractive force makes it difficult to maintain a desirably small (i.e., 1 mm) air gap between the primary and secondary. Further, the high attractive force may result in unacceptable vibration levels. Such control systems also typically employ a position encoder for controlling the position of the movable elevator door as a function of time in a door close or open operation. A drawback with door control systems which use a position encoder alone is that such encoders tend to be expensive and require high resolution and associated sophisticated signal processing.
It is therefore an object of the present invention to provide a control system for a linear motor elevator door operator which avoids the drawbacks and disadvantages of such prior control systems.